The present invention relates to a process and apparatus for internally coating a tubing formed of cellulose hydrate, particularly a fiber-reinforced tubing.
German Auslegeschrift No. 28 01 038 discloses a process for coating the inside surface of an endless tubing comprising a plastic film or a closely-woven fabric in which the tubing is filled with a supply of a liquid coating material and is then pulled through a gap formed between a pair of squeeze rollers which are so adjusted that the bulk of the coating material is held back and only a thin film of the coating material adhering to the inside surface of the tubing passes between the squeeze rollers. A number of guide rollers are arranged in series upstream of the pair of squeeze rollers, and the tubing is run around these guide rollers before it is passed between the pair of squeeze rollers which determine the thickness of the internal coating.
This prior art process is comparatively complicated, since the width of the gap between the two squeeze rollers must be very accurately adjusted. Minute, uneven or soiled places on the roller surfaces or variations in the thickness of the tubing material will result in non-uniform coatings.